Electric arc furnaces are utilized in the production of steel from scrap and the like. Smelting furnaces typically are designed as welded steel structures with water cooled walls and roof panels to protect the structure against the high temperatures of the furnace.
Currently, furnace roofs are provided with a plurality of generally pie-shaped cooling coil panels made from pipes which are removably mounted to a spider frame on the roof. In this way, failure of weld joints or the pipe may be repaired by removing and replacing one of the removable coil panels.
However, current cooling coil panels suffer several drawbacks. Each prior art panel is typically formed from lengths of pipe connected in a serpentine shape with gradually increasing lengths of pipe between end caps. Thus, in forming a "pie-shaped" panel, the point of the panel has a very short length of pipe between a pair of generally U-shaped end caps to return the pipe in the opposite direction. It can be seen that in such a design, many turns in the pipe are necessary to create the desired shape. Each such turn requires welded joints, which are the main areas of failure in such coolant coils. Each turn in the pipe also forms a restriction to water flow through the pipe, thereby reducing the velocity of water flow and increasing the pressure within the pipe.
Another problem with prior art pie-shaped designs for cooling coil panels lies in the fact that higher stresses and greater failure rates occur near the center of the roof section as compared to the outer peripheral region of the roof section. Thus, a pie-shaped panel is more likely to have only a small portion of the coil damaged by heat and stress near the point of the pie-shaped section. The replacement of such a panel thereby throws out a large portion of cooling coil which has not been damaged, thereby increasing maintenance costs and wasting materials.
Finally, the pie-shaped design of prior art coil panels utilizes a serpentine arrangement of pipe with the adjacent pipe lengths welded together and connected by caps with a tight 180.degree. turn. Such a serpentine design restricts expansion, and builds greater stresses on each weld because of the number of tight caps which are utilized.
It is therefore a general object of the present invention to provide an improved electric arc furnace roof with removable cooling coils.
Another object of the present invention is to provide a furnace roof with cooling coils which have fewer turns than conventional serpentine designs of pie-shaped panels.
Yet another object is to provide a furnace roof with a plurality of cooling coils designed to permit replacement of coils in high stress areas independently of coils in lower stress areas of the roof.
These and other objects will be apparent to those skilled in the art.